Water
splitting is the most potential method to produce hydrogen
energy, however, the conventional electrocatalysts encounter the hindrances
of high overpotential and low hydrogen production efficiency. Herein,
we report a carbon-based nanocomposite (denoted as CCW-x, x stands for the calcination temperature) derived
from watermelon peels and CoCl2, and the as-synthesized
CCW-x is used as the electrocatalyst. The overpotential
and the Tafel slope of CCW-700 for oxygen evolution reaction (OER)
is 237 mV at 10 mA cm–2 and 69.8 mV dec–1, respectively, both of which are lower than those of commercial
RuO2. For hydrogen evolution reaction (HER), the overpotential
of CCW-700 (111 mV) is higher than that of the widely studied Pt/C
(73 mV) but still lower than those of lots of carbon-based nanomaterials
(122–177 mV). In the light of CCW-700 is highly active for
both OER and HER, we assembled a water-splitting electrocatalyst by
employing nickel foam loaded with CCW-700 as the anode and cathode
in 1 M KOH. The water-splitting voltage is only 1.54 V for the CCW-700//CCW-700
electrodes and 1.62 V for the RuO2//Pt/C ones. Therefore,
the so-denoted CCW-x powder possesses good electrocatalytic
hydrogen production efficiency.
The highly ordered silver-coated colloidal crystals arrays and macroporous silver films were derived through an electrostatics-induced adsorption effect using polystyrene (PS) as templates. Carboxyl-modified PS microspheres were prepared by emulsifier-free emulsion polymerization using methacrylic acid (MAA) as the functional monomer. PS microspheres were self-assembled into close packing colloidal crystals of facecentered cubic arrays to the substrate with vertical deposition method. These colloidal crystals were modified using dopamine (DA) to form poly-dopamine (PDA) during its oxidative polymerization. Through electrostatic interaction, the silver nanoparticles were deposited and adsorbed onto the surfaces of colloidal crystals templates by exposing [Ag(NH3)2] + solution to infrared irradiation. Removal of the polymeric template by etching with methylbenzene solvent resulted in 3D ordered macroporous silver films. The structural and properties of the ordered silver-coated arrays and macroporous silver films were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-vis spectroscopy and surface-enhanced Raman spectroscopy (SERS). The results indicate that the prepared silver-coated arrays and macroporous silver films possess the features of ordered multilayer arrangement, uniformity and repeatability as well as an ideal SERS effect.
A series of new thermotropic liquid crystals (LCs) containing azobenzene units was synthesized. The structures of the compounds were characterized by means of NMR and FTIR spectroscopy. Their mesomorphic behaviors were investigated via differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Based on the POM and DSC measurements, the optical properties of the Razo-ester were tested using UV-vis spectroscopy. The azobenzene side chain displayed a strong ability to influence the formation of thermotropic LCs.
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